PAPR REDUCTION IN LAYERED-OFDMA OF LTE-A: A NEW PRECODING BASED ADAPTIVE UPLINK RA SYSTEM

This paper presents a new precoding based adaptive multi-carrier/single-carrier (MC/SC) uplink radio-access (RA) system with improved peak-to-average power ratio (PAPR) for layered orthogonal frequency division multiple access (Layered-OFDMA) of long term evolution advanced (LTE-A). The Discrete-Cosine transform (DCT) precoding is applied before subcarrier mapping and IFFT to reduce the high PAPR of the MC uplink system. The conventional SC system is implemented to sustain all the functionalities offered by the release 8 LTE. Extensive computer simulations have been performed to analyze the PAPR of the proposed system. The computer simulation results show that, the PAPR of DCT precoded MC signals is approximately same as that of conventional SC signals

Unified out-of-band emission reduction with linear complexity for OFDM

© 2014 IEEE. This paper proposes a unified out-of-band emission (OOBE) reduction framework with linear complexity for orthogonal frequency-division multiplexing (OFDM) systems. Unlike conventional spectral precoding approaches which use orthogonal precoding matrixes, this framework composes cancellation signals from the linear combinations of data symbols and minimizes the average OOBE power with a general least-squares solution. A joint frequency domain cancellation subcarrier and data domain cancellation symbol allocation scheme is also proposed for discrete Fourier transform precoded OFDM, by which the overall signal processing complexity of the OFDM transceiver is further reduced without impact on other system performance. The advantages of the proposed scheme is verified both analytically and by simulation as compared with some well-known low-complexity OOBE reduction schemes

PERFORMANCE EVALUATION OF A MULTICARRIER MIMO SYSTEM BASED ON DFT-PRECODING AND SUBCARRIER MAPPING

The ever-increasing end user demands are instigating the development of innovative methods targeting not only data rate enhancement but additionally better service quality in each subsequent wireless communication standard. This quest to achieve higher data rates has compelled the next generation communication technologies to use multicarrier systems e.g. orthogonal frequency division multiplexing (OFDM), while also relying on the multiple-input multiple-output (MIMO) technology. This paper is focused on implementing a MIMO-OFDM system and on using various techniques to optimize it in terms of the bit-error rate performance. The test case considered is a system implementation constituting the enabling technologies for 4G and beyond communication systems. The bit-error rate optimizations considered are based on preceding the OFDM modulation step by Discrete Fourier Transform (DFT) while also considering various subcarrier mapping schemes. MATLAB-based simulation of a 2 × 2 MIMO-OFDM system exhibits a maximum of 2 to 5 orders of magnitude reduction in bit-error rate due to DFT-precoding and subcarrier mapping respectively at high signal-to-noise ratio values in various environments. A 2-3dBs reduction in peak-to-average power ratio due to DFT-precoding in different environments is also exhibited in the various simulations

Performance Optimization of Peak to Average Power Ratio in FBMC Waveforms

High spectral efficiency and low computational complexity are the requirements of 5G wireless communication systems. They must also offer low PAPR (peak to average power ratio), low latency, and high throughput. In 5G it is not possible to realise all of these requirements through a single technique. One of the efforts is to look for a suitable technique for 5G. So, a suitable technique emerges whose name is Filter Bank Multicarrier (FBMC). But it has a high complexity, high Peak to Average Power (PAPR) and high out of band (OOB) leakage which results in inter-carrier interference and inter-channel interference. Also, due to high PAPR, mobile batteries are depleted more rapidly. So, a PAPR reduced method is needed. In this paper, a method of Pruned DFT Precoded FBMC to optimize the PAPR for different number of subcarriers. The performance evaluation in terms of bit error rate (BER) and spectral efficiency of OFDM, FBMC and Pruned DFT Precoded FBMC has been done in this paper.  In DFT Precoded FBMC, a DFT spreading matrix is multiplied with FBMC waveform and transmit only some part especially half of the DFT precoded matrix and rest remain zero by us. Monte Carlo simulation with one tap equalizer is used to validate our results

doi:10.1155/2011/614571 Research Article MMSE Beamforming for SC-FDMA Transmission over

which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We consider transmit beamforming for single-carrier frequency-division multiple access (SC-FDMA) transmission over frequency-selective multiple-input multiple-output (MIMO) channels. The beamforming filters are optimized for minimization of the sum of the mean-squared errors (MSEs) of the transmitted data streams after MIMO minimum mean-squared error linear equalization (MMSE-LE), and for minimization of the product of the MSEs after MIMO MMSE decision-feedback equalization (MMSE-DFE), respectively. We prove that for SC-FDMA transmission in both cases eigenbeamforming, diagonalizing the overall channel, together with a nonuniform power distribution is the optimum beamforming strategy. The optimum power allocation derived for MMSE-LE is similar in spirit to classical results for the optimum continuous-time transmit filter for linear modulation formats obtained by Berger/Tufts and Yang/Roy, whereas for MMSE-DFE the capacity achieving waterfilling strategy well known from conventional single-carrier transmission schemes is obtained. Moreover, we present a modification of the beamformer design to mitigate an increase of the peak-to-average power ratio (PAPR) which is in general associated with beamforming. Simulation results demonstrate the high performance of the proposed beamforming algorithms. 1

A Survey on Peak to Average Power Ratio Reduction Methods for LTE-OFDM

OFDM (Orthogonal Frequency Division Multiplexing) is generally preferred for high data rate transmission in digital communication. The Long-Term Evolution (LTE) standards for the fourth generation (4G) wireless communication systems. Orthogonal Frequency Division Multiple Access (OFDMA) and Single Carrier Frequency Division Multiple Access (SC-FDMA) are the two multiple access techniques which are generally used in LTE.OFDM system has a major shortcoming of high peak to average power ratio (PAPR) value. This paper explains different PAPR reduction techniques and presents a comparison of the various techniques based on theoretical results. It also presents a survey of the various PAPR reduction techniques and the state of the art in this area